A conventional semiconductor processing system contains one or more processing chambers and a means for moving a substrate between them. A substrate may be transferred between chambers by a robotic arm which can extend to pick up the substrate, retract and then extend again to position the substrate in a different destination chamber. FIG. 1 shows a schematic of a substrate processing chamber. Each chamber has a pedestal shaft 105 and pedestal 110 or some equivalent way of supporting the substrate 115 for processing.
A pedestal can be a heater plate in a processing chamber configured to heat the substrate. The substrate may be held by a mechanical, pressure differential or electrostatic means to the pedestal between when a robot arm drops off the substrate and when an arm returns to pick up the substrate. Lift pins are often used to elevate the wafer during robot operations.
One or more semiconductor fabrication process steps are performed in the chamber, such as annealing the substrate or depositing or etching films on the substrate. Dielectric films are deposited into complex topologies during some processing steps. Many techniques have been developed to deposit dielectrics into narrow gaps including variations of chemical vapor deposition techniques which sometimes employ plasma techniques. High-density plasma (HDP)-CVD has been used to fill many geometries due to the perpendicular impingement trajectories of the incoming reactants and the simultaneous sputtering activity. Some very narrow gaps, however, have continued to develop voids due, in part, to the lack of mobility following initial impact. Reflowing the material after deposition can fill the void but, if the dielectric has a high reflow temperature (like SiO2), the reflow process may also consume a non-negligible portion of a wafer's thermal budget.
By way of its high surface mobility, flow-able materials such as spin-on glass (SOG) have been useful in filling some of the gaps which were incompletely filled by HDP-CVD. SOG is applied as a liquid and cured after application to remove solvents, thereby converting material to a solid glass film. The gap-filling (gapfill) and planarization capabilities are enhanced for SOG when the viscosity is low. Unfortunately, low viscosity materials may shrink significantly during cure. Significant film shrinkage results in high film stress and delamination issues, especially for thick films.
Separating the delivery paths of two components can produce a flowable film during deposition on a substrate surface. FIG. 1 shows a schematic of a substrate processing system with separated delivery channels 125 and 135. An organo-silane precursor may be delivered through one channel and an oxidizing precursor may be delivered through the other. The oxidizing precursor may be excited by a remote plasma 145. The mixing region 120 of the two components occurs closer to the substrate 115 than alternative processes utilizing a more common delivery path. Since the films are grown rather than poured onto the surface, the organic components needed to decrease viscosity are allowed to evaporate during the process which reduces the shrinkage affiliated with a cure step. Growing films this way limits the time available for adsorbed species to remain mobile, a constraint which may result in deposition of nonuniform films. A baffle 140 may be used to more evenly distribute the precursors in the reaction region.
Gapfill capabilities and deposition uniformity benefit from high surface mobility which correlates with high organic content. Some of the organic content may remain after deposition and a cure step may be used. The cure may be conducted by raising the temperature of the pedestal 110 and substrate 115 with a resistive heater embedded in the pedestal.